The goal of this program project is to develop approaches for gene therapy of sickle cell disease based on gamma globin gene transfer. Our first objective is to produce vectors with which the transferred gamma globin gene will direct the production of at least 25% fetal hemoglobin in each red cell. This will be accomplished by combining the expertise in globin gene regulation of G. Stamatoyannopoulos' lab (Project l) with the expertise in vector development of the Dusty Miller lab (Vector Core). The second objective is to use an additive and combinatorial approach to increase the frequency of transduced stem cells to levels at which will be therapeutically meaningful. Towards achieving this goal first we will develop improved and practically applicable methods of item cell enrichment and apply culture innovations which will increase the rate of ex vivo stem cell transduction (Project 3). Second, we will produce new and optimal vectors for hemopoietic stem cell transduction (Project 2). Third, we will define the optimal conditions for transplantation of the transduced stem cells to patients. Project 3 addresses the question using peripheralized stem cells of primates while Project 4 is using the bone marrow transplantation model in the dog. Fourth, we will attempt to increase the in vivo frequency of transduced stem cells by in vivo selection. Two pilot projects and Project l locus on improving the means of in vivo selection by developing new dominant selectable markers conferring resistance to three different drugs. Projects 3 and 4 focus on the development of in vivo models for testing whether selective pressure can increase the frequency of transduced stem cells in large animals. This is a highly interactive and well coordinated program project bringing together investigators with expertise in molecular biology, vector construction, hemoglobinopathies, hematology, oncology, pharmacology and transplantation biology. It is expected that the research to be conducted by this program project will greatly enhance our ability to treat patients with beta chain hemoglobinopathies and specifically sickle cell disease.